The purpose of the project is to study alterations in the immune system caused by malignancy and chemotherapy. The status of the immune system in Hodgkin's and non-Hodgkin's lymphomas is being evaluated before, during, and after chemotherapy. Immunotherapy of nodular non-Hodgkin's lymphomas with MER will be evaluated and a randomized clinical trial with in vitro monitoring of the immune system is beginning. Animal models are being used to study mechanisms of drug immunosuppression. Infection in immunosuppressed host is being evaluated. A retrospective review of 156 cases of Candidiasis detected at post mortem examination is being completed. The mechanisms of action of Pentamidine is being studied in human, bacterial, trepanosomal sources. 5-Fluorocytosine has been shown to be converted to FdUMP in Candida Albicans with resultant depression of thymidylate synthetase activity.